QueryActivatableWorkflowsCommand Class

.NET Framework (current version)

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Represents the command that a generic host executes against an instance store to retrieve activation parameters. The generic host uses these activation parameters to create a workflow host, which in turn loads a runnable service instance.

Namespace:   System.Activities.DurableInstancing
Assembly:  System.Activities (in System.Activities.dll)


Public NotInheritable Class QueryActivatableWorkflowsCommand
	Inherits InstancePersistenceCommand


Initializes an instance of the QueryActivatableWorkflowsCommand class.


Indicates whether the command could attempt to acquire a lock on the instance. (Inherited from InstancePersistenceCommand.)


Returns a value that indicates whether the persistence provider may choose not to enlist in the ambient transaction (Transaction.Currnet) when executing this command. (Inherited from InstancePersistenceCommand.)


Gets the name of the persistence command.(Inherited from InstancePersistenceCommand.)


Determines whether the specified object is equal to the current object.(Inherited from Object.)


Serves as the default hash function. (Inherited from Object.)


Gets the Type of the current instance.(Inherited from Object.)


Returns a string that represents the current object.(Inherited from Object.)


Validates the command.(Inherited from InstancePersistenceCommand.)

An instance is activatable, if it is not in the suspended state or the completed state and satisfies the following conditions:

  • The instance is runnable. An instance in the persistence database is considered as runnable if it satisfies the following conditions:

    • The instance is unlocked and has a pending timer that has expired.

    • The instance is unlocked and its status is Executing.

    • The instance has an expired lock on it.

  • There is no workflow host capable of loading the instance is running on the local computer.

An instance store should periodically search for activatable workflow instances that belong to a workflow host that uses the store. It should raise the HasActivatableWorkflowEvent when it finds an activatable instance in the persistence store. If the instance store does not find an activatable instance in the persistence store, it should continue to monitor the persistence store for any activatable instances.

After raising the HasActivatableWorkflowEvent, the instance store should stop monitoring the persistence store for activatable instances until it receives and executes the QueryActivatableWorkflowsCommand. The monitoring continues only if the command execution does not return any activatable workflow instances.

When a generic host receives this event, it executes the QueryActivatableWorkflowsCommand against the instance store to obtain activation parameters required to create a workflow host. The generic host uses these activation parameters to create a workflow host, which in turn loads and runs the service instance. The activation parameters for the WAS activation type are: Site Name, Application Path (relative to the site), and Service Path (relative to the application). An instance store could return multiple sets of these three activation parameters.

A generic host is a host that has an XName parameter named ActivationType, which should be set to a value supported by the instance store. Currently, the SQL Workflow Instance Store supports generic hosts with ActivationType parameter set to value: WAS. If the ActivationType is not set at all, the SQL Workflow Instance Store treats the host as a generic host.


The Workflow Management Service that ships with the code named “Dublin” (Application Server Extensions for .NET 4.0) is a generic host that has the activation type set to WAS.

.NET Framework
Available since 4.0

Any public static ( Shared in Visual Basic) members of this type are thread safe. Any instance members are not guaranteed to be thread safe.

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